In recent years the supplying of hydrocarbon fuel, such as gasoline, to an internal combustion engine has progressed from gravity fuel feed and the use of cam-operated fuel pumps in an engine compartment, to the use of electrically-operated fuel pumps located in the main fuel tank of a vehicle. A further development has been the use of an upright cylindrical reservoir within the main fuel tank which houses the fuel pump in a substantially vertical position. The reservoir has a volume substantially larger than the pump housing and can serve to hold a supply of fuel independent of the fuel level in the main tank. In some fuel systems, the circuit includes a fuel line from the pump to the engine and a pressure regulator valve responds to excess pressure at the fuel rail (distributor) to by-pass fuel back to the reservoir. In other fuel systems, the reservoir receives fuel from the vapor outlets of the straight turbine pumps or the two-stage pumps and thus has the reserve fuel when needed.
As illustrated in U.S. Pat. No. 4,964,787 (Oct. 23, 1990), fuel from the tank is usually filtered through a sock filter connected to fuel pump inlet at the base of the reservoir. A sock valve is connected to the pump inlet.
As illustrated in U.S. Pat. No. 4,747,388 (May 31, 1988), a valve at the bottom of the reservoir is responsive to a diaphragm actuated by low fuel level in the main tank to cause the fuel pump to draw fuel from the reservoir itself. The diaphragm itself is a filter for fuel from the main tank.
It has been found that dirt particles get into the reservoir during assembly in the original installation. Also, the top of the reservoir is not always completely closed and objectionable particles may enter the reservoir from the surrounding atmosphere or fuel. Also, return fuel from the system entering the reservoir may pick up some contamination from the lines which can accumulate in the reservoir.